Timing and frame structure in an integrated access backhaul (IAB) network

ABSTRACT

Wireless communications systems and methods related to communicating in an integrated access backhaul (IAB) network are provided. A first wireless communication device of a multi-hop wireless network receives a first transmission timing adjustment command. The first wireless communication device communicates, with a second wireless communication device of the multi-hop wireless network based on at least the first transmission timing adjustment command, a first communication signal including backhaul data. The first wireless communication device communicates, with a third wireless communication device of the multi-hop wireless network based on the at least the first transmission timing adjustment command, a second communication signal.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 62/570,003, filed Oct. 9, 2017, whichis hereby incorporated by reference in its entirety as if fully setforth below and for all applicable purposes.

TECHNICAL FIELD

This application generally relates to wireless communication systems,and more particularly to communicating access data and backhaul dataover wireless links in an integrated access backhaul (IAB) network.Embodiments of the technology can enable and provide solutions andtechniques for wireless communication devices (e.g., base stations anduser equipment devices (UEs)) in an IAB network to maintainsynchronization and determine transmission and/or reception timelinesand frame structures for communications.

INTRODUCTION

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system). A wireless multiple-access communications system mayinclude a number of base stations (BSs), each simultaneously supportingcommunication for multiple communication devices, which may be otherwiseknown as user equipment (UE).

To meet the growing demands for expanded mobile broadband connectivity,wireless communication technologies are advancing from the LTEtechnology to a fifth generation (5G) new radio (NR) technology. 5G NRmay provision for access traffic and backhaul traffic at gigabit-levelthroughput. Access traffic refers to traffic between an access node(e.g., a base station) and a UE. Backhaul traffic refers to trafficamong access nodes and a core network.

BRIEF SUMMARY OF SOME EXAMPLES

The following summarizes some aspects of the present disclosure toprovide a basic understanding of the discussed technology. This summaryis not an extensive overview of all contemplated features of thedisclosure, and is intended neither to identify key or critical elementsof all aspects of the disclosure nor to delineate the scope of any orall aspects of the disclosure. Its sole purpose is to present someconcepts of one or more aspects of the disclosure in summary form as aprelude to the more detailed description that is presented later.

Embodiments of the present disclosure provide mechanisms forcommunicating in an integrated access backhaul (IAB) network employing amulti-hop topology (e.g., a spanning tree) to transport radio accesstraffic and backhaul traffic. For example, a BS or a UE may function asa relay node (e.g., a parent node or a child node) and at least one BSin direct communication with a core network may function as a root node.A relay node may exchange synchronization information with one or moreother relay nodes, adjust an internal synchronization reference, and/ordetermine transmission and/or reception timelines and/or framestructures (e.g., gap periods and cyclic prefixes (CPs)) forcommunicating radio access traffic and/or backhaul traffic with the oneor more other relay nodes.

For example, in an aspect of the disclosure, a method of wirelesscommunication includes receiving, by a first wireless communicationdevice of a multi-hop wireless network, a first transmission timingadjustment command. The method includes communicating, by the firstwireless communication device with a second wireless communicationdevice of the multi-hop wireless network based on at least the firsttransmission timing adjustment command, a first communication signalincluding backhaul data. The method includes communicating, by the firstwireless communication device with a third wireless communication deviceof the multi-hop wireless network based on the at least the firsttransmission timing adjustment command, a second communication signal.

In an additional aspect of the disclosure, a method of wirelesscommunication includes receiving, by a first wireless communicationdevice from one or more wireless communication devices of a multi-hopwireless network, synchronization information associated with the one ormore wireless communication devices. The method includes determining, bythe first wireless communication device, a transmission timingadjustment for a second wireless communication device of the one or morewireless communication devices based on at least some of thesynchronization information. The method includes transmitting, by thefirst wireless communication device, a message instructing the secondwireless communication device to communicate with a third wirelesscommunication device of the one or more wireless communication devicesbased on the transmission timing adjustment.

In an additional aspect of the disclosure, an apparatus includes atransceiver configured to receive a first transmission timing adjustmentcommand, wherein the apparatus is associated with a multi-hop wirelessnetwork. The transceiver is further configured to communicate, with afirst wireless communication device of the multi-hop wireless networkbased on at least the first transmission timing adjustment command, afirst communication signal including backhaul data. The transceiver isfurther configured to communicate, with a second wireless communicationdevice of the multi-hop wireless network based on the at least the firsttransmission timing adjustment command, a second communication signal.

In an additional aspect of the disclosure, an apparatus includes atransceiver configured to receive, from one or more wirelesscommunication devices of a multi-hop wireless network, synchronizationinformation associated with the one or more wireless communicationdevices. The apparatus further includes a processor configured todetermine a transmission timing adjustment for a first wirelesscommunication device of the one or more wireless communication devicesbased on at least some of the synchronization information. Thetransceiver is further configured to transmit a message instructing thefirst wireless communication device to communicate with a secondwireless communication device of the one or more wireless communicationdevices based on the transmission timing adjustment.

Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication network according toembodiments of the present disclosure.

FIG. 2 illustrates an integrated access backhaul (IAB) network accordingto embodiments of the present disclosure.

FIG. 3 illustrates an IAB network according to embodiments of thepresent disclosure.

FIG. 4 illustrates an IAB network topology according to embodiments ofthe present disclosure.

FIG. 5 illustrates an IAB network resource sharing method according toembodiments of the present disclosure.

FIG. 6 is a block diagram of an exemplary user equipment (UE) accordingto embodiments of the present disclosure.

FIG. 7 is a block diagram of an exemplary base station (BS) according toembodiments of the present disclosure.

FIG. 8 is a timing diagram illustrating a scheduling method for awireless access network according to embodiments of the presentdisclosure.

FIG. 9 is a timing diagram illustrating a scheduling method for an IABnetwork according to embodiments of the present disclosure.

FIG. 10 is a timing diagram illustrating a scheduling method for an IABnetwork according to embodiments of the present disclosure.

FIG. 11 is a signaling diagraming illustrating an IAB communicationmethod according to embodiments of the present disclosure.

FIG. 12 is a signaling diagraming illustrating an IAB communicationmethod according to embodiments of the present disclosure.

FIG. 13 illustrates a distributed synchronization method according toembodiments of the present disclosure.

FIG. 14 illustrates a centralized synchronization method transmissionmethod according to embodiments of the present disclosure.

FIG. 15 is a signaling diagraming illustrating a distributedsynchronization method according to embodiments of the presentdisclosure.

FIG. 16 is a signaling diagraming illustrating a centralizedsynchronization method according to embodiments of the presentdisclosure.

FIG. 17 illustrates a wireless backhaul network according to embodimentsof the present disclosure.

FIG. 18 illustrates a traffic routing overlay in a wireless backhaulnetwork according to embodiments of the present disclosure.

FIG. 19 illustrates a synchronization overlay in a wireless backhaulnetwork according to embodiments of the present disclosure.

FIG. 20 illustrates a synchronization overlay in a wireless backhaulnetwork according to embodiments of the present disclosure.

FIG. 21 is a signaling diagram illustrating an IAB communication methodaccording to embodiments of the present disclosure.

FIG. 22 is a flow diagram of a method for communicating in an IABnetwork according to embodiments of the present disclosure.

FIG. 23 is a flow diagram of a method for managing synchronizationreferences in an IAB network according to embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form to avoidobscuring such concepts.

Techniques described herein may be used for various wirelesscommunication networks. These networks can include code-divisionmultiple access (CDMA), time-division multiple access (TDMA),frequency-division multiple access (FDMA), orthogonal frequency-divisionmultiple access (OFDMA), single-carrier FDMA (SC-FDMA) and othernetworks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). CDMA2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies, such as a next generation network including 5GNR. Some 5G NR networks (aka (e.g., 5th Generation) (5G) operating inmmWave bands) can operate in a variety of frequency bands (e.g., mmWaveor sub-6 Ghz) that covers both licensed and unlicensed spectrum.

The present disclosure describes mechanisms and techniques forcommunicating in an IAB network. An IAB network may include acombination of wireless access links between BSs and UEs and wirelessbackhaul links between the BSs. The IAB network may employ a multi-hoptopology (e.g., a spanning tree) for transporting access traffic andbackhaul traffic. One of the BSs may be configured with an optical fiberconnection in communication with a core network. In some scenarios a BSmay function as an anchoring node (e.g., a root node) to transportbackhaul traffic between a core network and the IAB network. In otherscenarios one BS may serve the role of a central node in conjunctionwith connections to a core network. And in some arrangements, BSs andthe UEs may be referred to as relay nodes in the network.

BSs can serve a variety of roles in a network in either a static ordynamic nature. For example, each BS may have one or more parent nodes.These parent nodes can include other BSs. BSs may have one or more childnodes, which may include other BSs and/or UEs. The UEs may function aschild nodes. Parent nodes may function as access nodes to child nodes.Parent nodes may be referred to as access functionality (ACF)-nodes.Child nodes may function as UEs to parent nodes and may be referred toas UE functionality (UEF)-nodes. BSs may function as an ACF-node whencommunicating with a child node and may function as a UEF-node whencommunicating with a parent node. The disclosed embodiments generallyprovide signaling mechanisms for nodes in an IAB network to maintainsynchronization and determine transmission and/or reception timelinesand frame structures for communications. Given a variety of topologicalarrangements of IAB networks and constraints/demands placed on a networksynchronization helps overall network functions and performance forpositive user experiences.

In an embodiment, a relay node may maintain and track one or moresynchronization references for communications in a network. Asynchronization reference can be an internal reference at a node or anexternal reference such as a global positioning system (GPS) connectedto the node. Relay nodes may exchange synchronization information, forexample, via messages or reference signals. A central entity can collectsynchronization reports from the relay nodes and configure the relaynodes with synchronization adjustments. Thus, a relay node may adjust aninternal synchronization reference based on synchronization informationreceived from other relay nodes, timing information received from a GPS,adjustments received from a central entity, and/or adjustments receivedfrom a particular relay node selected by the central entity.Accordingly, the present disclosure provides techniques for over-the-air(OTA) synchronization in a multi-hop IAB network.

In an embodiment, when a relay node functions as an ACF-node, the relaynode may determine or utilize a number of parameters. These can includegap periods, transmit timing, receiving time, and/or cyclic prefix (CP)mode (e.g., a normal CP mode or an extended CP (ECP) mode) forcommunicating with corresponding UEF-nodes. In an embodiment, a centralentity may determine adjustment information including gap periods,transmit timing adjustment, receiving time adjustment, and/or CP modefor the relay nodes to communicate with each other and may provide theadjustment information to the relay nodes.

Aspects of the technology discussed herein can provide several benefits.For example, the use of ACF-UEF relationships among the relay nodes canleverage at least some of the current LTE technologies, such asscheduling and timing advance mechanisms. The use of multiplesynchronization references and exchange of synchronization informationallows the nodes to synchronize with each other and synchronize to areliable synchronization source (e.g., a GPS). The flexibility ofselecting between an ECP mode, a gap period insertion, and/or a transmitand/or receive timing adjustment can avoid interference and increaseresource utilization efficiency. These and other benefits are more fullyrecognized and discussed below.

FIG. 1 illustrates a wireless communication network 100 according toembodiments of the present disclosure. The network 100 includes aplurality of BSs 105, a plurality of UEs 115, and a core network 130.The network 100 may be a LTE network, a LTE-A network, a millimeter wave(mmW) network, a new radio (NR) network, a 5G network, or any othersuccessor network to LTE.

The BSs 105 may wirelessly communicate with the UEs 115 via one or moreBS antennas. Each BS 105 may provide communication coverage for arespective geographic coverage area 110. In 3GPP, the term “cell” canrefer to this particular geographic coverage area of a BS and/or a BSsubsystem serving the coverage area, depending on the context in whichthe term is used. In the example shown in FIG. 1, the BSs 105 a, 105 b,105 c, 105 d, and 105 e are examples of macro BSs for the coverage areas110 a, 110 b, 110 c, 110 d, and 110 e, respectively.

Communication links 125 shown in the network 100 may include uplink (UL)transmissions from a UE 115 to a BS 105, or downlink (DL) transmissions,from a BS 105 to a UE 115. The communication links 125 are referred toas wireless access links. The UEs 115 may be dispersed throughout thenetwork 100, and each UE 115 may be stationary or mobile. A UE 115 mayalso be referred to as a mobile station, a subscriber station, a mobileunit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology. AUE 115 may also be a cellular phone, a personal digital assistant (PDA),a wireless modem, a wireless communication device, a handheld device, atablet computer, a laptop computer, a cordless phone, a personalelectronic device, a handheld device, a personal computer, a wirelesslocal loop (WLL) station, an Internet of things (IoT) device, anInternet of Everything (IoE) device, a machine type communication (MTC)device, an appliance, an automobile, or the like.

The BSs 105 may communicate with the core network 130 and with oneanother via optical fiber links 134. The core network 130 may provideuser authentication, access authorization, tracking, Internet Protocol(IP) connectivity, and other access, routing, or mobility functions. Atleast some of the BSs 105 (e.g., which may be an example of an evolvedNodeB (eNB), a next generation NodeB (gNB), or an access node controller(ANC)) may interface with the core network 130 through the backhaullinks 134 (e.g., S1, S2, etc.) and may perform radio configuration andscheduling for communication with the UEs 115. In various examples, theBSs 105 may communicate, either directly or indirectly (e.g., throughcore network 130), with each other over the backhaul links 134 (e.g.,X1, X2, etc.).

Each BS 105 may also communicate with a number of UEs 115 through anumber of other BSs 105, where the BS 105 may be an example of a smartradio head. In alternative configurations, various functions of each BS105 may be distributed across various BSs 105 (e.g., radio heads andaccess network controllers) or consolidated into a single BS 105.

In some implementations, the network 100 utilizes orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the UL. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, or the like. Eachsubcarrier may be modulated with data. In general, modulation symbolsare sent in the frequency domain with OFDM and in the time domain withSC-FDM. The spacing between adjacent subcarriers may be fixed, and thetotal number of subcarriers (K) may be dependent on the systembandwidth. The system bandwidth may also be partitioned into subbands.

In an embodiment, the BSs 105 can assign or schedule transmissionresources (e.g., in the form of time-frequency resource blocks) for DLand UL transmissions in the network 100. DL refers to the transmissiondirection from a BS 105 to a UE 115, whereas UL refers to thetransmission direction from a UE 115 to a BS 105. The communication canbe in the form of radio frames. A radio frame may be divided into aplurality of subframes, for example, about 10. Each subframe can bedivided into slots, for example, about 2. In a frequency-divisionduplexing (FDD) mode, simultaneous UL and DL transmissions may occur indifferent frequency bands. For example, each subframe includes a ULsubframe in a UL frequency band and a DL subframe in a DL frequencyband. In a time-division duplexing (TDD) mode, UL and DL transmissionsoccur at different time periods using the same frequency band. Forexample, a subset of the subframes (e.g., DL subframes) in a radio framemay be used for DL transmissions and another subset of the subframes(e.g., UL subframes) in the radio frame may be used for ULtransmissions.

The DL subframes and the UL subframes can be further divided intoseveral regions. For example, each DL or UL subframe may havepre-defined regions for transmissions of reference signals, controlinformation, and data. Reference signals are predetermined signals thatfacilitate the communications between the BSs 105 and the UEs 115. Forexample, a reference signal can have a particular pilot pattern orstructure, where pilot tones may span across an operational bandwidth orfrequency band, each positioned at a pre-defined time and a pre-definedfrequency. For example, a BS 105 may transmit cell-specific referencesignals (CRSs) and/or channel state information-reference signals(CSI-RSs) to enable a UE 115 to estimate a DL channel. Similarly, a UE115 may transmit sounding reference signals (SRSs) to enable a BS 105 toestimate a UL channel. Control information may include resourceassignments and protocol controls. Data may include protocol data and/oroperational data. In some embodiments, the BSs 105 and the UEs 115 maycommunicate using self-contained subframes. A self-contained subframemay include a portion for DL communication and a portion for ULcommunication. A self-contained subframe can be DL-centric orUL-centric. A DL-centric subframe may include a longer duration for DLcommunication tha UL communication. A UL-centric subframe may include alonger duration for UL communication tha UL communication.

In an embodiment, a UE 115 attempting to access the network 100 mayperform an initial cell search by detecting a primary synchronizationsignal (PSS) from a BS 105. The PSS may enable synchronization of periodtiming and may indicate a physical layer identity value. The UE 115 maythen receive a secondary synchronization signal (SSS). The SSS mayenable radio frame synchronization, and may provide a cell identityvalue, which may be combined with the physical layer identity value toidentify the cell. The SSS may also enable detection of a duplexing modeand a cyclic prefix length. Some systems, such as TDD systems, maytransmit an SSS but not a PSS. Both the PSS and the SSS may be locatedin a central portion of a carrier, respectively. After receiving the PSSand SSS, the UE 115 may receive a master information block (MIB), whichmay be transmitted in the physical broadcast channel (PBCH). The MIB maycontain system bandwidth information, a system frame number (SFN), and aPhysical Hybrid-ARQ Indicator Channel (PHICH) configuration. Afterdecoding the MIB, the UE 115 may receive one or more system informationblocks (SIBs). For example, SIB1 may contain cell access parameters andscheduling information for other SIBs. Decoding SIB1 may enable the UE115 to receive SIB2. SIB2 may contain radio resource configuration (RRC)configuration information related to random access channel (RACH)procedures, paging, physical uplink control channel (PUCCH), physicaluplink shared channel (PUSCH), power control, SRS, and cell barring.After obtaining the MIB and/or the SIBs, the UE 115 can perform randomaccess procedures to establish a connection with the BS 105. Afterestablishing the connection, the UE 115 and the BS 105 can enter anormal operation stage, where operational data may be exchanged.

FIG. 2 illustrates an IAB network 200 according to embodiments of thepresent disclosure. The network 200 is substantially similar to thenetwork 100. For example, the BSs 105 communicates with the UEs 115 overthe wireless access links 125. However, in the network 200, only one BS(e.g., the BS 105 c) is connected to an optical fiber backhaul link 134.The other BSs 105 a, 105 b, 105 d, and 105 e wirelessly communicate witheach other and with the BS 105 c over wireless backhaul links 234. TheBS 105 c connected to the optical fiber backhaul link 134 may functionas an anchor for the other BSs 105 a, 105 b, 105 d, and 105 e tocommunicate the core network 130, as described in greater detail herein.The wireless access links 125 and the wireless backhaul links 234 mayshare resources for communications in the network 200. The network 200may also be referred to as a self-backhauling network. The network 200can improve wireless link capacity, reduce latency, and reducedeployment cost.

FIG. 3 illustrates an IAB network 300 according to embodiments of thepresent disclosure. The network 300 is similar to the network 200 andillustrates the use of millimeter wave (mmWav) frequency band forcommunications. In the network 300, a single BS (e.g., the BS 105 c) isconnected to an optical fiber backhaul link 134. The other BSs 105 a,105 b, 105 d, and 105 e communicate with each other and with the BS 105c using directional beams 334, for example, over the wireless links 234.The BSs 105 may also communicate with the UEs 115 using narrowdirectional beams 325, for example, over the wireless links 125. Thedirectional beams 334 may be substantially similar to the directionalbeams 325. For example, the BSs 105 may use analog beamforming and/ordigital beamforming to form the directional beams 334 and 325 fortransmission and/or reception. Similarly, the UEs 115 may use analogbeamforming and/or digital beamforming to form the directional beams 325for transmission and/or reception. The use of mmmWav can increasenetwork throughput and reduce latency. The use of narrow directionalbeams 334 and 325 can minimize inter-link interference. Thus, thenetwork 300 can improve system performance.

FIG. 4 illustrates an IAB network topology 400 according to embodimentsof the present disclosure. The topology 400 can be employed by thenetworks 200 and 300. For example, the BSs 105 and the UEs 115 can beconfigured to form a logical spanning tree configuration as shown in thetopology 400 for communicating access traffic and/or backhaul traffic.The topology 400 may include an anchor 410 coupled to an optical fiberlink 134 for communication with a core network (e.g., the core network130). The anchor 410 may correspond to the BS 105 c in the networks 200and 300.

The topology 400 includes a plurality of logical levels 402. In theexample of FIG. 4, the topology 400 includes three levels 402, shown as402 a, 402 b, and 402 c. In some other embodiments, the topology 400 caninclude any suitable number of levels 402 (e.g., two, three, four, five,or six). Each level 402 may include a combination of UEs 115 and BSs 105interconnected by logical links 404, shown as 404 a, 404 b, and 404 c.For example, a logical link 404 between a BS 105 and a UE 115 maycorrespond to a wireless access link 125, whereas a logical link 404between two BSs 105 may correspond to a wireless backhaul link 234. TheBSs 105 and the UEs 115 may be referred to as relay nodes in thetopology 400.

The nodes (e.g., the BSs 105) in the level 402 a can function as relaysfor the nodes in the level 402 b, for example, to relay backhaul trafficbetween the nodes and the anchor 410. Similarly, the nodes (e.g., theBSs 105) in the level 402 b can function as relays for the nodes in thelevel 402 c. For example, the nodes in the level 402 a are parent nodesto the nodes in the level 402 b, and the nodes in the level 402 c arechild nodes to the nodes in level 402 b. The parent nodes may functionas ACF-nodes and the child nodes may function as UEF-nodes.

For example, a BS 105 may implement both ACF and UEF and may function asan ACF-node and an UEF-node depending on which node the BS iscommunicating with. For example, a BS 105 (shown as pattern-filled) inthe level 402 b may function as an access node when communicating with aBS 105 or a UE 115 in the level 402 c. Alternatively, the BS 105 mayfunction as a UE when communicating with a BS 105 in the level 402 a.When a communication is with a node in a higher level or with a lessnumber of hops to the anchor 410, the communication is referred to as aUL communication. When a communication is with a node in a lower levelor with a greater number of hops to the anchor 410, the communication isreferred to as a DL communication. In some embodiments, the anchor 410may allocate resources for the links 404. Mechanisms for scheduling ULand DL transmissions and/or allocating resources based on the topology400 are described in greater detail herein.

FIG. 5 illustrates an IAB network resource sharing method 500 accordingto embodiments of the present disclosure. The method 500 illustratesresource partitioning for use in the topology 400. In FIG. 5, the x-axisrepresents time in some constant units. The method 500 time-partitionresources in an IAB network (e.g., the networks 200 and 300) intoresources 510 and 520. The resources 510 and 520 can includetime-frequency resources. For example, each resource 510 or 520 mayinclude a number of symbols (e.g., OFDM symbols) in time and a number ofsubcarriers in frequency. In some embodiments, each resource 510 or 520shown may correspond to a subframe, a slot, or a transmission timeinterval (TTI), which may carry one media access control (MAC) layertransport block.

As an example, the method 500 may assign the resources 510 to the links404 a and 404 c in the topology 400 for communicating UL and/or DLtraffic. The method 500 may assign the resources 520 to the links 404 bin the topology 400 for communicating UL and/or DL traffic. Thetime-partitioning of the resources in the alternating manner shown inthe method 500 can reduce interference between the different levels 402,overcome the half-duplex constraint, and reduce transmit-receive gapperiods.

FIG. 6 is a block diagram of an exemplary UE 600 according toembodiments of the present disclosure. The UE 600 may be a UE 115 asdiscussed above. As shown, the UE 600 may include a processor 602, amemory 604, an IAB communication module 608, a transceiver 610 includinga modem subsystem 612 and a radio frequency (RF) unit 614, and one ormore antennas 616. These elements may be in direct or indirectcommunication with each other, for example via one or more buses.

The processor 602 may include a central processing unit (CPU), a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a controller, a field programmable gate array (FPGA) device,another hardware device, a firmware device, or any combination thereofconfigured to perform the operations described herein. The processor 602may also be implemented as a combination of computing devices, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The memory 604 may include a cache memory (e.g., a cache memory of theprocessor 602), random access memory (RAM), magnetoresistive RAM (MRAM),read-only memory (ROM), programmable read-only memory (PROM), erasableprogrammable read only memory (EPROM), electrically erasableprogrammable read only memory (EEPROM), flash memory, solid state memorydevice, hard disk drives, other forms of volatile and non-volatilememory, or a combination of different types of memory. In an embodiment,the memory 604 includes a non-transitory computer-readable medium. Thememory 604 may store instructions 606. The instructions 606 may includeinstructions that, when executed by the processor 602, cause theprocessor 602 to perform the operations described herein with referenceto the UEs 115 in connection with embodiments of the present disclosure.Instructions 606 may also be referred to as code. The terms“instructions” and “code” should be interpreted broadly to include anytype of computer-readable statement(s). For example, the terms“instructions” and “code” may refer to one or more programs, routines,sub-routines, functions, procedures, etc. “Instructions” and “code” mayinclude a single computer-readable statement or many computer-readablestatements.

The IAB communication module 608 may be implemented via hardware,software, or combinations thereof. For example, the IAB communicationmodule 608 may be implemented as a processor, circuit, and/orinstructions 606 stored in the memory 604 and executed by the processor602. The IAB communication module 608 may be used for various aspects ofthe present disclosure. For example, the IAB communication module 608 isconfigured to maintain multiple synchronization references, providesynchronization information (e.g., including timing and/or frequency)associated with the synchronization references to other nodes (e.g., theBSs 105), receive synchronization information from other nodes, receivesynchronization adjustment commands, receive scheduling information(e.g., gap periods, transmission timing, and/or reception timing),adjust synchronization references based on the received synchronizationinformation and/or the received commands, and/or communicate with othernodes based on received scheduling information, as described in greaterdetail herein.

As shown, the transceiver 610 may include the modem subsystem 612 andthe RF unit 614. The transceiver 610 can be configured to communicatebi-directionally with other devices, such as the BSs 105. The modemsubsystem 612 may be configured to modulate and/or encode the data fromthe memory 604 and/or the IAB communication module 608 according to amodulation and coding method (MCS), e.g., a low-density parity check(LDPC) coding method, a turbo coding method, a convolutional codingmethod, a digital beamforming method, etc. The RF unit 614 may beconfigured to process (e.g., perform analog to digital conversion ordigital to analog conversion, etc.) modulated/encoded data from themodem subsystem 612 (on outbound transmissions) or of transmissionsoriginating from another source such as a UE 115 or a BS 105. The RFunit 614 may be further configured to perform analog beamforming inconjunction with the digital beamforming. Although shown as integratedtogether in transceiver 610, the modem subsystem 612 and the RF unit 614may be separate devices that are coupled together at the UE 115 toenable the UE 115 to communicate with other devices.

The RF unit 614 may provide the modulated and/or processed data, e.g.data packets (or, more generally, data messages that may contain one ormore data packets and other information), to the antennas 616 fortransmission to one or more other devices. This may include, forexample, transmission of reservation signals, reservation responsesignals, and/or any communication signal according to embodiments of thepresent disclosure. The antennas 616 may further receive data messagestransmitted from other devices. This may include, for example, receptionof synchronization information, synchronization adjustment commands,and/or scheduling adjustment information according to embodiments of thepresent disclosure. The antennas 616 may provide the received datamessages for processing and/or demodulation at the transceiver 610. Theantennas 616 may include multiple antennas of similar or differentdesigns in order to sustain multiple transmission links. The RF unit 614may configure the antennas 616.

FIG. 7 is a block diagram of an exemplary BS 700 according toembodiments of the present disclosure. The BS 700 may be a BS 105 asdiscussed above. A shown, the BS 700 may include a processor 702, amemory 704, a IAB communication module 708, a transceiver 710 includinga modem subsystem 712 and a RF unit 714, and one or more antennas 716.These elements may be in direct or indirect communication with eachother, for example via one or more buses.

The processor 702 may have various features as a specific-typeprocessor. For example, these may include a CPU, a DSP, an ASIC, acontroller, a FPGA device, another hardware device, a firmware device,or any combination thereof configured to perform the operationsdescribed herein. The processor 702 may also be implemented as acombination of computing devices, e.g., a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The memory 704 may include a cache memory (e.g., a cache memory of theprocessor 702), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, asolid state memory device, one or more hard disk drives, memristor-basedarrays, other forms of volatile and non-volatile memory, or acombination of different types of memory. In some embodiments, thememory 704 may include a non-transitory computer-readable medium. Thememory 704 may store instructions 706. The instructions 706 may includeinstructions that, when executed by the processor 702, cause theprocessor 702 to perform operations described herein. Instructions 706may also be referred to as code, which may be interpreted broadly toinclude any type of computer-readable statement(s) as discussed abovewith respect to FIG. 7.

The IAB communication module 708 may be implemented via hardware,software, or combinations thereof. For example, the IAB communicationmodule 708 may be implemented as a processor, circuit, and/orinstructions 706 stored in the memory 604 and executed by the processor702. The IAB communication module 708 may be used for various aspects ofthe present disclosure. For example, the IAB communication module 708 isconfigured to maintain multiple synchronization references, providesynchronization information (e.g., including timing and/or frequency)associated with the synchronization references to other nodes (e.g., theBSs 105 and the UEs 115 and 600), receive synchronization informationfrom other nodes, receive synchronization adjustment commands, adjustsynchronization references based on the received synchronizationinformation or the received commands, receive scheduling information(e.g., gap periods, transmission timing, and/or reception timing) forcommunication with nodes at a higher level (e.g., less hops away from ananchor 410 than the BS 700), determine scheduling information forcommunication with nodes at a lower level (e.g., more hops away from ananchor 410 than the BS 700), and/or communicate with nodes based on thereceived scheduling information and the determined schedulinginformation, as described in greater detail herein.

As shown, the transceiver 710 may include the modem subsystem 712 andthe RF unit 714. The transceiver 710 can be configured to communicatebi-directionally with other devices, such as the UEs 115 and/or anothercore network element. The modem subsystem 712 may be configured tomodulate and/or encode data according to a MCS, e.g., a LDPC codingmethod, a turbo coding method, a convolutional coding method, a digitalbeamforming method, etc. The RF unit 714 may be configured to process(e.g., perform analog to digital conversion or digital to analogconversion, etc.) modulated/encoded data from the modem subsystem 712(on outbound transmissions) or of transmissions originating from anothersource such as a UE 115. The RF unit 714 may be further configured toperform analog beamforming in conjunction with the digital beamforming.Although shown as integrated together in transceiver 710, the modemsubsystem 712 and the RF unit 714 may be separate devices that arecoupled together at the BS 105 to enable the BS 105 to communicate withother devices.

The RF unit 714 may provide the modulated and/or processed data, e.g.data packets (or, more generally, data messages that may contain one ormore data packets and other information), to the antennas 716 fortransmission to one or more other devices. This may include, forexample, transmission of information to complete attachment to a networkand communication with a camped UE 115 according to embodiments of thepresent disclosure. The antennas 716 may further receive data messagestransmitted from other devices and provide the received data messagesfor processing and/or demodulation at the transceiver 710. The antennas716 may include multiple antennas of similar or different designs inorder to sustain multiple transmission links.

FIGS. 8-10 illustrate various timelines for communicating over wirelessaccess links (e.g., the wireless access links 125) and wireless backhaullinks (e.g., the wireless backhaul links 234). In FIGS. 8-10, the x-axesrepresent time in some constant units. The illustrated timelines setforth how various method embodiments can be implemented and aredescribed in detail below.

FIG. 8 is a timing diagram illustrating a scheduling method 800 for awireless access network according to embodiments of the presentdisclosure. The method 800 may be employed by a BS (e.g., the BSs 105)to communicate with a UE (e.g., the UEs 115) over a wireless access link(e.g., the wireless access links 125). The method 800 is illustratedwith one UE for simplicity of discussion, but may be scaled to includeany suitable number of UEs (e.g., five, ten, twenty, or more thantwenty).

The method 800 generally shows BS/UE communications via the verticallines shown in the drawing. As shown, in the method 800, the BS maytransmit DL signals 810 to the UE, for example, based on a timingreference of the BS (e.g., as shown by the DL transmit (Tx) timeline802). The UE may receive the DL signals 810 after a propagation delay830 as shown by the DL receive (Rx) timeline 804. The UE may transmit ULsignals 820 to the BS, for example, based on a timing reference providedby the BS as shown by the UL Tx timeline 806.

To determine a schedule for the UE, the BS may estimate a round triptime (RTT) 832 between the BS and the UE, for example, based on a randomaccess procedure. The propagation delay 830 may correspond to half ofthe RTT 832. The BS may transmit a timing advance (TA) command to the UEinstructing the UE to transmit at an earlier time than an expectedscheduled transmit time. The UE is expected to track the DL timing ofthe BS and adjust the UE's UL timing based the DL timing. For example,the BS may schedule the UE to transmit at a particular time according tothe timeline 802. The UE may transmit at an earlier time than thescheduled transmit time based on the TA command so that the transmissioncan reach the BS at an arrival time according to the BS's timeline 802.

In addition, the BS may schedule the UE by providing a gap period forthe UE to switch between transmit and receive. For example, the BS mayschedule the UE to transmit a UL signal 820 sometime after a receptiontime of the DL signal 810 instead of immediately after a reception ofthe DL signal 810. As shown, there is a gap period 834 between thereception of a DL signal 810 and the transmission of a UL signal 820.While the method 800 is described in the context of a BS communicatingwith a UE over a wireless access link, the method 800 can be applied toa BS communicating with another BS over a wireless backhaul link, asdescribed in greater detail herein.

FIG. 9 is a timing diagram illustrating a scheduling method 900 for anIAB network according to embodiments of the present disclosure. FIG. 9illustrates communications between multiple components as represented bythe vertical lines. The method 900 may be employed by a BS (e.g., theBSs 105) to communicate with a UE (e.g., the UEs 115) over a wirelessaccess link (e.g., the wireless access links 125) or another BS over awireless backhaul link (e.g., the wireless backhaul links 234) in an IABnetwork (e.g., the networks 200 and 300). The method 900 illustratesthree nodes R1, R2, and R3 in three levels (e.g., the levels 402) forsimplicity of discussion, but may be scaled to include any suitablenumber nodes (e.g., five, ten, twenty, or more than twenty) configuredin any suitable number of levels (e.g., four, five, or more than five).

Nodes R1, R2, and R3 may correspond to a portion of the topology 400.For example, node R1 may be at a hop h1 (e.g., the levels 402) withrespect to the anchor 410, where h1 is a positive integer. The method900 may be used in conjunction with the method 500. For example, node R1and the node R2 may correspond to BSs 105, and the node R3 maycorrespond to a BS 105 or a UE 115. The DL₁ Tx timeline 902, the DL₁ Rxtimeline 904, and the UL₁ Tx timeline 906 between the node R1 and thenode R2 are similar to the timeline 802, 804, and 806, respectively. Insome scenarios, the node R1 may function as a parent node or an ACF-nodeto the node R2. The node R1 may transmit DL signals 910 according to atiming reference of the node R1. The DL signals 910 may arrive at thenode R2 after a propagation delay. The node R1 may transmit a TA commandto the node R2. The node R2 may track the DL timing of the node R1,receive the TA command, and transmit UL signals 920 based on the TAcommand.

In some scenarios, nodes of FIG. 9 may communicate with each other basedon scheduling (e.g., timing-based scheduling). For example, the node R2can communicate with the node R3 (e.g., a child node or a UEF-node tothe node R2). The node R2 can select a DL transmit timing reference(e.g., DL₂ Tx) for transmitting DL signals 930 to the node R3. FIG. 9illustrates three options 932, 934, and 936 for the DL₂ Tx timeline 908.

In the first option 932, the node R2 may use a single transmit timingreference by aligning the DL transmit timing of the node R2 to the ULtransmit timing of the node R2.

In the second option 934, the node R2 may use two transmit timingreferences, one for UL transmissions based on instructions from the nodeR1 and another one for DL transmissions. The node R2 may align the DLtransmit timing of the node R2 to a DL transmit timing of a parent nodeor an ACF-node (e.g., the node R1) of the node R2.

In the third option 936, the node R2 may use two transmit timingreferences, one for UL transmissions based on instructions from the nodeR1 and another one for DL transmissions. The node R2 may align the DLtransmit timing of the node R2 to the DL receive timing (e.g., areception time of the DL signals 910) of the node R2.

The node R2 may select any one of the options 932, 934, and 936.However, the first option 932 and the third option 936 may lead to alarge timing misalignment between nodes in the network depending on thenumber of hops (e.g., the levels 402) due to the accumulative effects ofpropagation delays (e.g., the delay 830) from one hop to the next. Thesecond option 934 may provide the least amount timing misalignment sinceall DL transmit timing in the network may be aligned to the DL transmittiming of a top-level node (e.g., the anchor 410).

After selecting a timing reference for DL transmit, the node R2 mayschedule UL and/or DL communications with the node R3. The node R2 mayinclude a gap period in a schedule as required for the node R3 to switchbetween receive and transmit. The node R2 may further measureinterference (e.g., cross-link interference) in the network, monitortransmissions (e.g., transmission error rates) in the network, andschedule the UL transmissions based on the measured interference (e.g.,to minimize cross-link interference) and the monitored information(e.g., to minimize transmission error rates).

FIG. 10 is a timing diagram illustrating a scheduling method 1000 for anIAB network according to embodiments of the present disclosure. FIG. 10illustrates communications between multiple components as represented bythe vertical lines. The method 1000 may be employed by BSs (e.g., theBSs 105) to communicate with each other over wireless backhaul links(e.g., the wireless backhaul links 234) in an JAB network (e.g., thenetworks 200 and 300). The method 1000 illustrates a node R2 having twoparent nodes R1 and R2 (e.g., in a mesh topology) for simplicity ofdiscussion, but may be scaled to include any suitable number of parentnodes (e.g., three, four, five, or six). The nodes R1, R2, and R3 maycorrespond to the BSs 105. The nodes R1, R2, and R3 may correspond to aportion of the topology 400. For example, the node R1 may be at a hop h1with respect to the anchor 410 and the node R2 may be at a hop h2 withrespect to the anchor 410, where h1 and h2 are positive integers. Themethod 1000 may be used in conjunction with the method 500.

In the method 1000, the node R1 may transmit DL signals 1010 accordingto a timing reference of the node R1 as shown by the DL₁ Tx timeline1001. The DL signals 1010 may arrive at the node R3 after a propagationdelay as shown by the DL₁ Rx timeline 1003. The node R2 may transmit DLsignals 1020 according to a timing reference of the node R2 as shown bythe DL₂ Tx timeline 1002. The DL signals 1020 may arrive at the node R3after a propagation delay as shown by the DL₂ Rx timeline 1005.

The node R3 may transmit UL signals 1030 based on a timing referenceinstructed by the node R1 (e.g., via a TA command) as shown by the UL₁Tx timeline 1004. Similarly, the node R3 may transmit UL signals 1040based on a timing reference instructed by the node R2 (e.g., via a TAcommand) as shown by the UL₂ Tx timeline 1006.

When the node R3 employs the second option 934 described in the method900 with respect to FIG. 9, the node R3 may align the DL transmit timingof the node R3 to an average timing of the parent nodes R1 and R2. Whenemploying the second option 934, the maximum gap period required maycorrespond to a maximum RTT in the network, for example, a maximum RTT1050 from the parent nodes R1 and R2 to the node R3 as shown. Afteraligning or selecting a timing reference, the node R3 may determine gapperiods for scheduling communications with child nodes or UEF-nodes ofthe node R3 as a function of the timing reference, as described ingreater detail herein.

As shown in the methods 800, 900, and 1000, the present disclosureprovides techniques for timing alignment across multi-hop IAB networks.In an example, DL transmission timing is aligned across IAB nodes (e.g.,the BSs 105 and the relay nodes 1310) and IAB donors (e.g., the anchor410, the BSs 105, and the relay nodes 1310)) as shown by the option 934.In an example, DL and UL transmission timing is aligned within anIAB-node as shown by the option 932.

FIG. 11 is a signaling diagraming illustrating an IAB communicationmethod 1100 according to embodiments of the present disclosure. Themethod 1100 is implemented among relay nodes R1, R2, and R3. The node R1may correspond to a BS (e.g., the BSs 105 and 700 and the anchor 410)and may function as an ACF-node to the nodes R2 and R3. The nodes R2 andR3 may correspond to BSs and/or UEs (e.g., the UEs 115 and 600) and mayfunction as UEF-nodes to the node R1. Steps of the method 1100 can beexecuted by computing devices (e.g., a processor, processing circuit,and/or other suitable component) of the relay nodes. As illustrated, themethod 1100 includes a number of enumerated steps, but embodiments ofthe method 1100 may include additional steps before, after, and inbetween the enumerated steps. In some embodiments, one or more of theenumerated steps may be omitted or performed in a different order. Useof the label “step” is to describe an action or activity as opposed tosetting a prescribed or required order of events.

At step 1110, the node R1 determines a first gap period (e.g., theperiod 834) for communicating with the node R2. For example, the node R1may receive a report from the node R2. The reports may includecapability information, a transmit-receive switching requirement, asynchronization reference switching requirement, or schedulinginformation of the node R2. The capability information may include aUE-category or a power class of the node R2 and/or frequency bands,radio access technologies (RATs), measurement and reporting supported bythe node R2, and/or features supported by the node R2. Thetransmit-receive switching requirement refers to the amount of timerequired for the node R2 to switch from a transmit mode to a receivemode or from a receive mode to a transmit mode. The synchronizationreference switching requirement refers to the amount of time for thenode R2 to switching between two or more synchronization references. Thenode R1 may determine the first gap period based on the report.

At step 1120, the node R1 determines a second gap period (e.g., theperiod 834) for communicating with the node R3, for example, based on atransmit-receive switching of the node R3.

At step 1130, the node R1 communicates with the node R2 based on thefirst gap period. For example, the node R1 may determine a DLtransmission time for transmitting to the node R2 and/or a ULtransmission time for the node R2 based on the first gap period.

At step 1140, the node R1 communicates with the node R3 based on thesecond gap period. For example, the node R1 may determine a DLtransmission time for transmitting to the node R3 and/or a ULtransmission time for the node R3 based on the second gap period.

In some embodiments, the first gap period and the second gap period canbe indicated in downlink control information (DCI) along with schedulinginformation. For example, in the context of LTE or NR, the node R1 maytransmit a physical downlink control channel (PDCCH) signal indicating aschedule for communicating a signal with the node R2. The PDCCH signalmay include a DCI indicating a gap period. Alternatively, gap periodscan be indicated in other DCI, media access control (MAC) controlelement (CEs), MIBs, SIBs, and/or a RRC messages.

As can be seen, in the method 1100, an ACF-node or a parent node (e.g.,the node R1) may determine a UEF-specific gap period for communicatingwith a UEF-node or a child node (e.g., the nodes R2 and R3).

FIG. 12 is a signaling diagraming illustrating an IAB communicationmethod 1200 according to embodiments of the present disclosure. Themethod 1200 is implemented among relay nodes R1, R2, and R3. The node R1may correspond to a BS (e.g., the BSs 105 and 700 and the anchor 410)and may function as an ACF-node to the nodes R2 and R3. The nodes R2 andR3 may correspond to BSs and/or UEs (e.g., the UEs 115 and 600) and mayfunction as UEF-nodes to the node R1. Steps of the method 1200 can beexecuted by computing devices (e.g., a processor, processing circuit,and/or other suitable component) of the relay nodes. As illustrated, themethod 1200 includes a number of enumerated steps, but embodiments ofthe method 1200 may include additional steps before, after, and inbetween the enumerated steps. In some embodiments, one or more of theenumerated steps may be omitted or performed in a different order.

The method 1200 may improve resource utilization efficiency compared tothe method 1100. For example, gap periods can be wasteful in terms ofresource utilization since gap periods are idle periods with notransmission. When a parent node (e.g., the node R1) determines that allof its child nodes (e.g., the nodes R2 and R3) require a certain gapperiod, the parent node may adjust (e.g., advance or delay) a timingreference of the parent node. In other words, the parent node may adjusta frame boundary or a slot boundary for communicating with the childnodes.

Alternatively, when the parent node determines that multiple gap periodsin a slot for communicating with the child nodes, the parent node mayswitch from a normal cyclic prefix (CP) mode to an extended CP (ECP)mode. CP refers to the prefixing of a symbol with a repetition of an endof the symbol. CP is used in OFDM symbols to mitigate inter-symbolinterference (ISI). An ECP refers to a CP with an extended time durationcompared to a normal CP.

At step 1210, the node R1 adjusts the node R1's timing reference. Forexample, the node R1 may determine the adjustment such that theadjustment may not cause interference to other relay nodes in thenetwork or create scheduling conflicts with other relay nodes. Theadjustment may be a delaying of and advancing of the timing reference oran inclusion of an ECP.

At step 1220, the node R1 communicates with the node R2 based on theadjusted timing reference.

At step 1230, the node R1 communicates with the node R3 based on theadjusted timing reference.

Accordingly, the present disclosure provides techniques for alignmentsbetween IAB nodes and/or IAB donors or within an IAB node based on aslot-level-alignment or a symbol-level-alignment.

FIGS. 13-16 illustrate various mechanisms for maintaining and/orrefining synchronization in an IAB network (e.g., the networks 200 and300), for example, based on a timing reference of an anchor (e.g., theanchor 410), a relay node (e.g., the BSs 105 and the UEs 115) with a GPSconnection, a selected relay node, and/or a central entity.

FIG. 13 illustrates a distributed synchronization method 1300 accordingto embodiments of the present disclosure. The method 1300 may beemployed by BSs (e.g., the BSs 105) and UEs (e.g., the UEs 115) in anIAB network (e.g., the network 100). The method 1300 illustrates fourrelay nodes 1310 with one relay node including a GPS 1320 for simplicityof discussion, but may be scaled to include any suitable number of relaynodes (e.g., five, six, ten, or more than ten) and/or GPS connections(e.g., three, four, five, or six).

In the method 1300, the node R1 1310 may correspond to a BS and thenodes R2, R3, and R4 1310 can be a BS or a UE. In an embodiment, thenode R1 1310 may be an anchor (e.g., the anchor 410) in the network.Each of the nodes 1310 may maintain one or more synchronizationreferences and may communicate synchronization information (e.g., timinginformation and/or frequency information) with each other. Each node1310 may adjust the node 1310's synchronization references based onsynchronization information received from other nodes.

The nodes 1310 may exchange synchronization information related tointernal timing references with each other. In addition, the node R21310 may transmit synchronization information based on a timing providedby the GPS 1320 to the node R1 1310. The nodes 1310 may receivesynchronization information from one or more sources (e.g., other nodes1310 and/or the GPS 1320) and may adjust an internal timing referencebased on the received synchronization information.

FIG. 14 illustrates a centralized synchronization method 1400 accordingto embodiments of the present disclosure. The method 1400 may beemployed by BSs (e.g., the BSs 105) and UEs (e.g., the UEs 115) in anIAB network (e.g., the network 100). The method 1400 is substantiallysimilar to the method 1300, but employs a central entity 1410 todetermine adjustments for synchronization references of the nodes 1310.The central entity 1410 may be a logical entity and may be physicallymapped to any node in a network, for example, an anchoring node, a relaynode 1310, or a dedicated node.

In the method 1400, the central entity 1410 may collect synchronizationinformation from the nodes 1310. The central entity 1410 may determinesynchronization adjustments for the nodes 1310 based on the collectedsynchronization information. The central entity 1410 may transmit thedetermined synchronization adjustments to corresponding nodes 1310.

FIG. 15 is a signaling diagraming illustrating a distributedsynchronization method 1500 according to embodiments of the presentdisclosure. The method 1500 is implemented between a relay node R1 (e.g.the BSs 105 and the UEs 115 and the nodes 1310) and other relay nodes(e.g. the BSs 105 and the UEs 115 and the nodes 1310) in an IAB network(e.g., the network 100). The node R1 may be coupled to a GPS (e.g., theGPS 1320). The other relay nodes may include a combination of UEF-nodesof the node R1 and ACF-nodes of the node R1. The method 1500 may employsimilar mechanisms as described in the method 1300 with respect to FIG.13. Steps of the method 1500 can be executed by computing devices (e.g.,a processor, processing circuit, and/or other suitable component) of therelay nodes. As illustrated, the method 1500 includes a number ofenumerated steps, but embodiments of the method 1500 may includeadditional steps before, after, and in between the enumerated steps. Insome embodiments, one or more of the enumerated steps may be omitted orperformed in a different order.

At step 1510, the GPS transmits timing information to the node R1.

At step 1520, one or more other relay nodes may transmit messages to thenode R1. Each message may include synchronization information associatedwith a synchronization reference (e.g., a GPS 1320 or an internalsynchronization reference) of a corresponding relay node. Thesynchronization information can include timing information or frequencyinformation. The message may indicate an amount of timing adjustmentand/or an amount of frequency adjustment for the node R1. In someembodiments, the messages are LTE or NR MAC CEs.

At step 1530, one or more other relay nodes may transmit synchronizationreference signals, for example, based on synchronization references atcorresponding relay nodes. The synchronization reference signals may belayer 1 (L1) (e.g., physical layer) signals including a predeterminedsignal sequence. In some embodiments, the synchronization referencesignals may be carried in NR synchronization signal (SS) blocks.

In an embodiment, the synchronization reference signals and/or themessages may be transmitted based on a semi-static schedule. In anembodiment, the synchronization reference signals and/or the messagesmay be transmitted in response to a request from the node R1.

At step 1540, the node R1 may adjust synchronization references of thenode R1 based on the timing information received from the GPS, thesynchronization information in the received messages, and/ormeasurements (e.g., timing and/or frequency measurements) of thereceived synchronization reference signals.

In an embodiment, the node R1 may adjust the synchronization referencesof the node R1 upon detecting a difference between the synchronizationreferences of the node R1 and the received synchronization referencesignals exceeding a threshold.

In some embodiments, there can be a priority level associated with eachsource of the synchronization information. The information about thepriority level may be included in each corresponding synchronizationmessage indicating a source of the synchronization information, forexample, whether the synchronization information is based on a GPS or aninternal synchronization reference. Additionally or alternatively, theinformation about the priority level may be indicated through othermessages, by other nodes in the system, or acquired from upper layer. Insome embodiments, each message can include a priority level indicating ahop count or level (e.g., the level 402) at which a corresponding nodeis located. Thus, a node (e.g., the node R1) receiving thesynchronization information may adjust the node's internalsynchronization reference as a function of the priority levels. Forexample, the node may adjust an internal synchronization reference basedon an average determined from the highest priority synchronizationinformation.

FIG. 16 is a signaling diagraming illustrating a centralizedsynchronization method 1600 according to embodiments of the presentdisclosure. The method 1600 is implemented between a central entity(e.g., the central entity 1410) and relay nodes (e.g. the BSs 105 andthe UEs 115) in an IAB network (e.g., the network 100). The method 1600may employ similar mechanisms as described in the method 1400 withrespect to FIG. 14. Steps of the method 1600 can be executed bycomputing devices (e.g., a processor, processing circuit, and/or othersuitable component) of the relay nodes. As illustrated, the method 1600includes a number of enumerated steps, but embodiments of the method1600 may include additional steps before, after, and in between theenumerated steps. In some embodiments, one or more of the enumeratedsteps may be omitted or performed in a different order.

At step 1610, the relay nodes may transmit synchronization informationto the central entity. The synchronization information may correspond totiming and/or frequency information of a synchronization reference(e.g., a GPS 1320 or an internal synchronization reference) of acorresponding relay node.

At step 1620, the central entity may determine adjustments forsynchronization references of the relay nodes based on the receivedsynchronization information.

At step 1630, the central entity may transmit the determinedsynchronization adjustments to corresponding relay nodes. For example,the central entity may instruct a first relay node to communicate with asecond relay node using a particular adjustment. In some embodiments,the adjustments may include gap periods, transmit timing adjustments,receive timing adjustments, synchronization timing adjustments, and/orsynchronization frequency adjustments. In some embodiments, the centralentity may further receive reports from the relay nodes. The reports mayinclude capability information, scheduling information, transmit-receiveswitching requirements, synchronization reference switching requirementsassociated with the relay nodes. The central entity may determine thegap periods and/or cyclic prefix configurations (e.g., normal CP or ECP)based on the reports. In some embodiments, the synchronizationinformation and the adjustments may be carried in NR or LTE RRCmessages.

FIG. 17 illustrates a wireless backhaul network 1700 according toembodiments of the present disclosure. The network 1700 may be similarto the networks 200 and 300. The network 1700 includes a plurality ofrelay nodes 1310 shown as R1 to R11. Some of the nodes 1310 (e.g., R5and R8) may include connections to GPSs 1320. The network 1700 mayemploy the topology 400 to establish multi-hop relay links 1702. Thenode R1 1310 may be an anchoring node (e.g., the anchor 410) incommunication with a core network (e.g., the network 130) via an opticalfiber link (e.g., the optical fiber link 134). The node R1 1310 mayfunction as an intermediary to relay backhaul traffic between the corenetwork and the other nodes 1310.

FIG. 18 illustrates a traffic routing overlay 1800 over the wirelessbackhaul network 1700 according to embodiments of the presentdisclosure. The traffic routing overlay 1800 includes traffic routes1802 established among the nodes 1310 for routing traffic in the network1700. The traffic routes 1802 may or may not be overlaid on top of allthe links 1702. For example, while the node R7 1310 and the node R8 1310can be connected by a link 1702, the traffic routing overlay 1800 doesnot include a traffic route 1802 between the node R7 1310 and the nodeR8 1310. The traffic routing overlay 1800 may partition and allocateresources for the traffic routes 1802 (e.g., overlaid over the links1702) to transport traffic among the nodes 1310, for example, using themethod 500. The traffic routing overlay 1800 can include various networkcontrol and/or management operations such as keep alive and linkmaintenance operations.

FIG. 19 illustrates a synchronization overlay 1900 over the wirelessbackhaul network 1700 according to embodiments of the presentdisclosure. The synchronization overlay 1900 is based on the trafficrouting overlay 1800. The synchronization overlay 1900 reuses thetraffic routes 1802 established by the traffic routing overlay 1800 andresources allocated by the traffic routing overlay 1800 to transportsynchronization information and/or adjustment instructions in the amongthe nodes 1310. The synchronization overlay 1900 can support on-demandexchange of synchronization information and/or adjustments. Thesynchronization overlay 1900 can also leverage network controls (e.g.,keep alive and link maintenance protocols) supported by the trafficrouting overlay 1800.

FIG. 20 illustrates a synchronization overlay 2000 over the wirelessbackhaul network 1700 according to embodiments of the presentdisclosure. Instead of reusing the traffic routing overlay 1800 as inthe overlay 1900, the overlay 2000 may establish routes 2002 over thelinks 1702. The routes 2002 may be different from the traffic routes1802. For example, the overlay 2000 may establish the routes 2002 basedon synchronization sources (e.g., the GPSs 1320) available in thenetwork 1700. Thus, the overlay 2000 may provide better utilization ofsynchronization sources, but may be required to allocate resources,determine schedules, and/or other network controls separate from theoverlay 1800.

When a network (e.g., the networks 200 and 300) employs the overlay 1900(e.g., reusing the traffic overlay 1800), UEF-nodes in the network canprovide synchronization feedbacks to corresponding ACF-nodes, forexample, via MAC CEs. ACF-nodes in the network may receive the feedbacksfrom corresponding UEF-nodes and adjusts synchronization referencesbased on the feedbacks.

When a network employs the overlays 1900 or 2000, relay nodes in thenetwork can send physical reference signals (e.g., in synchronizationsignal blocks (SSBs)). Other relay nodes in the network may receive thephysical reference signals and may adjust corresponding synchronizationreferences based on measurements of the received physical referencesignals, for example, for frequency tracking.

FIG. 21 is a signaling diagraming illustrating a synchronization method2100 according to embodiments of the present disclosure. The method 2100is implemented between a relay node R1 (e.g. the nodes 1310 and the BSs105 and 700) and other relay nodes (e.g. the nodes 1310, the BSs 105 and700, and the UEs 115 and 600) in an IAB network (e.g., the network 100).The other relay nodes may be UEF-nodes or child nodes of the node R1.The node R1 and the other relay nodes may be part of the overlay 1900 or2000. Steps of the method 2100 can be executed by computing devices(e.g., a processor, processing circuit, and/or other suitable component)of the relay nodes. As illustrated, the method 2100 includes a number ofenumerated steps, but embodiments of the method 2100 may includeadditional steps before, after, and in between the enumerated steps. Insome embodiments, one or more of the enumerated steps may be omitted orperformed in a different order.

At step 2110, the node R1 determines a first synchronization referenceadjustment for one or more internal synchronization references of thenode R1. The first adjustment may be relatively small, for example, afew samples or less than a symbol time period. The node R1 may adjustthe internal synchronization references and continue to communicate withthe other relay nodes.

At step 2120, the node R1 communicates with the other relay nodes basedon the adjusted synchronization references.

At step 2130, the other relay nodes may track the adjustment based onthe communications with the node R1. For example, a relay node mayreceive a communication or synchronization signal from the node R1 andmay detect the adjustment from the received communication signal. Thus,the relay node may adjust an internal synchronization reference of thenode based on the detected adjustment.

At step 2140, after a period of time, the node R1 determines a secondsynchronization reference adjustment for the internal synchronizationreferences. The second adjustment may be relatively large, for example,greater than a symbol time period. The node R1 may determine that aresynchronization is required from the other relay nodes.

At step 2150, the node R1 transmits a resynchronization request to theother relay nodes. The node R1 may transmit the resynchronizationrequest in a broadcast mode. The node R1 may additionally indicateresource and/or configuration information (e.g., a set ofsynchronization reference signals or synchronization pulses) that theother relay nodes may use for the resynchronization. In someembodiments, the node R1 may further indicate a resynchronizationconfiguration, for example, including an amount of the adjustment and/orwhen the adjustment becomes effective (e.g., an offset time period or anumber of slots with respect to a transmission time of the request).

At step 2160, upon receiving the resynchronization request, the otherrelay nodes may perform resynchronization based on the request. Forexample, a relay node may receive synchronization reference signalsbased on the resources and/or configuration indicated in the request andmay adjust corresponding internal synchronization references at a starttime corresponding to the offset time period or slot number indicated inthe request. While the method 2100 is described in the context of timesynchronization and adjustment, the method 2100 can be applied toperform frequency synchronization and adjustment.

FIG. 22 is a flow diagram of a method 2200 for communicating in an IABnetwork according to embodiments of the present disclosure. The networkmay be similar to the networks 200, 300, and 1700 and may be configuredwith the topology 400 and/or the overlays 1800, 1900, and 2000. Steps ofthe method 2200 can be executed by a computing device (e.g., aprocessor, processing circuit, and/or other suitable component) of awireless communication device, such as the BSs 105 and 700 and the UEs115 and 600. The method 2200 may employ similar mechanisms as in themethods 500, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, and2100 described with respect to FIGS. 5, 8, 9, 10, 11, 12, 13, 14, 15,16, and 21, respectively. As illustrated, the method 2200 includes anumber of enumerated steps, but embodiments of the method 2200 mayinclude additional steps before, after, and in between the enumeratedsteps. In some embodiments, one or more of the enumerated steps may beomitted or performed in a different order.

At step 2210, the method 2200 includes receiving, by a first wirelesscommunication device, synchronization information from one or morewireless relay devices. The first wireless communication device and theone or more wireless relay devices may correspond to the relay nodes1310.

At step 2220, the method 2200 includes adjusting, by the first wirelesscommunication device, one or more synchronization references based on atleast some of the synchronization information.

At step 2230, the method 2200 includes communicating, by the firstwireless communication device with the one or more wireless relaydevices, communication signals based on the one or more adjustedsynchronization references. The communication signals can include acombination of backhaul traffic and access traffic.

In an embodiment, the first wireless communication device may be a BSand the one or more wireless relay devices can include parent nodes(e.g., ACF-nodes) and/or child nodes (e.g., UEF-nodes) of the firstwireless communication devices. For example, the one or more wirelessrelay devices may include a combination of UEs (e.g., child nodes) andother BSs (e.g., child nodes and/or parent nodes). The UEs may be servedby the BS over wireless access links (e.g., the wireless access links125). The BS may relay backhaul traffic for other BSs over wirelessbackhaul links (e.g., the wireless backhaul links 234).

In an embodiment, the first wireless communication device may receivethe synchronization information by receiving, from a first wirelessrelay device of the one or more wireless relay devices, a messageincluding at least one of timing information associated with asynchronization reference of the first wireless relay device, frequencyinformation associated with the synchronization reference of the firstwireless relay device, capability information of the first wirelessrelay device, scheduling information of the first wireless relay device,a transmit-receive switching requirement of the first wireless relaydevice, or a synchronization reference switching requirement of thefirst wireless relay device.

In an embodiment, the first wireless communication device may receivethe synchronization information by receiving, from a first wirelessrelay device of the one or more wireless relay devices, asynchronization reference signal that is based on a synchronizationreference of the first wireless relay device. The first wirelesscommunication device can determine frequency offset and/or timing offsetbased on measurements of the received synchronization reference signals.

In an embodiment, the synchronization information may include prioritylevel information. The priority level information may include the sourceof the synchronization information, for example, whether thesynchronization information is obtained from a GPS or an internalsynchronization reference of a corresponding relay node. The prioritylevel information may also include a hop count indicating the number ofhops (e.g., the levels 402) with respect to original sources ofcorresponding synchronization references. Thus, the first wirelesscommunication device can adjust the one or more synchronizationreferences as a function of the priority levels.

In an embodiment, the first wireless communication device may receivethe synchronization information from a central entity (e.g., the centralentity 1410). In an embodiment, the first wireless communication devicemay further receive at least one of timing information or frequencyinformation from an external synchronization source and may adjust theone or more synchronization references further based on the at least oneof timing information or frequency information. The externalsynchronization source may be a GPS (e.g., the GPS 1320) or asynchronization source provided by another radio access technology(RAT). In some embodiments, the first wireless communication device mayrequest for the synchronization information. In some other embodiments,the first wireless communication device may receive the synchronizationinformation based on a semi-static schedule. In an embodiment, the firstcommunication device may transmit synchronization information associatedwith the one or more synchronization references based on at least one ofa schedule, a synchronization information request, a measurement of theone or more synchronization references, or the adjusting of the one ormore synchronization references.

In an embodiment, the first wireless communication device may relaybackhaul traffic of the one or more wireless relay devices to ananchoring wireless communication device (e.g., the anchor 410) incommunication with a core network (e.g., the core network 130) via anoptical fiber link (e.g., the optical fiber link 134). The firstwireless communication device may communicate with the one or morewireless relay devices based on a DL transmit timing of the anchoringwireless communication device, for example, using the second option 934shown in the method 900.

In an embodiment, the first wireless communication device maycommunicate with the one or more wireless relay devices usingUEF-specific gap period (e.g., the gap period 834) based on eachwireless relay device's capability (e.g., transmit-receive switchingtime). For example, the first wireless communication device maydetermine a first gap period based on a capability parameter of a firstwireless relay device of the one or more wireless relay devices. Thefirst wireless communication device may determine a second gap periodbased on a capability parameter of a second wireless relay device of theone or more wireless relay devices, the second gap period different fromthe first gap period. The first wireless communication device maycommunicate with the first wireless relay device and the second wirelessrelay device based on the first gap period and the second gap period,respectively.

In an embodiment, the first wireless communication device can determinea gap period based on measurements and indication received from parentnodes (e.g., ACF-nodes) and/or child nodes (e.g., the UEF-nodes) of thefirst wireless communication device. In an embodiment, the firstwireless communication device can determine a gap period based onschedules of the first wireless communication device or schedules ofother relay nodes. In an embodiment, the first wireless communicationdevice can determine a gap period based on commands received from acentral entity.

In some embodiments, a gap period can be located at any position withina slot, for example, at the beginning of a slot, at the end of a slot,or in the middle of the slot. The gap period can be network-wide,cell-specific, and/or UEF-specific. In some embodiments, a gap periodmay change from slot to slot. In some embodiments, a gap period can besemi-statically configured with a semi-persistent pattern.

In an embodiment, the first wireless communication device maysimultaneously communicate with a first wireless relay device and asecond wireless relay device of the one or more wireless relay devices.The first wireless communication may communicate with the first wirelessrelay device using a first synchronization reference and may communicatewith the second wireless relay device using a second synchronizationreference that is different from the first synchronization reference.

In an embodiment, the first wireless communication device may switchfrom a normal CP to an ECP during the communication based on capabilityparameters of the one or more wireless relay devices. When the firstwireless communication device multiplexes communication with multiplerelay devices, there may be a need to extend the duration of a CP (e.g.,to an ECP) to accommodate the different timings of the multiple relaydevices in order to avoid ISI.

In an embodiment, the first wireless communication device may usedifferent antenna sub-arrays and different digital chains whencommunicating simultaneously with multiple wireless relay devices. Insuch an embodiment, the first wireless communication device may not berequired to switch to an ECP mode. In another embodiment, the firstwireless communication device may use different antenna sub-arrays witha single digital chain or a single antenna sub-array with multi-fingerbeamforming. In such an embodiment, the first wireless communicationdevice may be required to switch to an ECP mode and multiplex thecommunications, for exampl, using frequency-division multiplexing (FUM).

In an embodiment, the first wireless communication device maycommunicate with a first wireless relay device of the one or morewireless relay devices, a first communication signal of thecommunication signals during a first time period based on a firstsynchronization reference of the one or more synchronization references.The first wireless communication device may communicate with a secondwireless relay device of the one or more wireless relay devices, asecond communication signal of the communication signals during a secondtime period subsequent to the first time period based on a secondsynchronization reference of the one or more synchronization referencesthat is different than the first synchronization reference. For example,the first wireless communication device may transmit and/or receive areference signal (e.g., a CSI-RS), a control signal, and/or a datasignal by sweeping transmit and/or receive beams towards differentdirections over consecutive time periods. In some embodiments, commonresources may be allocated to multiple relay devices for transmittingsynchronization signals or beam references signals. Since differentrelay devices can have different propagation delays, the use of ECP maybe beneficial to accommodate the different delays.

While a schedule may accommodate timing misalignment among differentnodes and/or avoid ISI by introducing gap periods or using an ECP mode,there is a tradeoff between the use of ECP and gap periods. The use ofECP increases overheads in all symbols within a slot. However, when aschedule requires multiple gap periods within a slot, the use of ECP maybe suitable. Conversely, when a schedule does not require multipleswitching between different synchronization references, the use of gapperiods may be suitable. For example, a relay node may sweep multipledirections towards one node based on a first synchronization referenceand then sweep multiple directions towards another node based on asecond synchronization reference. In such a scenario, the relay node mayrequire a single gap period between the two sweeps, which may be moreefficient than using an ECP for all symbols.

In an embodiment, the first wireless communication device can determinewhether to select a normal CP or an ECP based on measurements andindication received from parent nodes (e.g., ACF-nodes) and/or childnodes (e.g., the UEF-nodes) of the first wireless communication device,schedules of the first wireless communication device, schedules of otherrelay nodes, and/or commands received from a central entity.

FIG. 23 is a flow diagram of a method 2300 for managing synchronizationreferences in an IAB network according to embodiments of the presentdisclosure. The network may be similar to the networks 200, 300, and1700 and may be configured with the topology 400 and/or the overlays1800, 1900, and 2000. Steps of the method 2300 can be executed by acomputing device (e.g., a processor, processing circuit, and/or othersuitable component) of a wireless communication device, such as the BSs105 and 700 and the central entity 1410. The method 2300 may employsimilar mechanisms as in the methods 500, 800, 900, 1000, 1100, 1200,1300, 1400, 1500, 1600, and 2100 described with respect to FIGS. 5, 8,9, 10, 11, 12, 13, 14, 15, 16, and 21, respectively. As illustrated, themethod 2300 includes a number of enumerated steps, but embodiments ofthe method 2300 may include additional steps before, after, and inbetween the enumerated steps. In some embodiments, one or more of theenumerated steps may be omitted or performed in a different order.

At step 2310, the method 2300 includes receiving, by a central entityfrom one or more wireless relay devices (e.g., the BSs 105 and 700, theUEs 115 and 600, and the relay nodes 1310), synchronization informationassociated with the one or more wireless relay devices. Thesynchronization information may include frequency information and/ortiming information associated with synchronization references of the oneor more wireless relay devices.

At step 2320, the method 2300 includes determining, by the centralentity, a synchronization reference adjustment based on at least some ofthe synchronization information. The adjustment may include a gapperiod, a cyclic prefix configuration, a timing synchronizationadjustment, a frequency synchronization adjustment, a transmit timingadjustment, and/or a receive timing adjustment.

At step 2330, the method 2300 includes transmitting, by the centralentity, a message instructing a first wireless relay device of the oneor more wireless relay devices to communicate with a second wirelessrelay device of the one or more wireless relay devices based on thesynchronization reference adjustment.

In an embodiment, the central entity can collect reports from the one ormore wireless relay devices. The reports can include at least one ofcapability information of the one or more wireless relay devices,scheduling information of the one or more wireless relay devices,transmit-receive switching requirements of the one or more wirelessrelay devices, synchronization reference switching requirements of theone or more wireless relay devices, or priority levels associated withsynchronization reference sources of the one or more wireless relaydevices. The central entity can determine at least one of the gap periodor the cyclic prefix configuration for the first wireless relay deviceto communicate with the second wireless relay device based on thereports.

In an embodiment, the first wireless communication device and the secondwireless communication devices may both be BSs, where the adjustment isfor backhaul communication. For example, the first wirelesscommunication device may be a parent node or an ACF-node of the secondwireless communication device. Alternatively, the first wirelesscommunication device may be a child node or a UEF-node of the secondwireless communication device.

In an embodiment, the first wireless communication device may be a BSand the second wireless communication device may be a UE, where theadjustment is for access communication.

In another embodiment, the first wireless communication device may be aUE and the second wireless communication device may be a BS, where theadjustment is for access communication.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of [at least one of A, B, or C]means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Embodiments of the present disclosure further include acomputer-readable medium having program code recorded thereon, theprogram code comprising code for causing a first wireless communicationdevice to receive synchronization information associated with one ormore wireless relay devices; code for causing the first wirelesscommunication device to adjust one or more synchronization referencesbased on at least some of the synchronization information; and code forcausing the first wireless communication device to communicate, with theone or more wireless relay devices, communication signals based on theone or more adjusted synchronization references, wherein at least one ofthe communication signals includes backhaul traffic.

The computer-readable medium further includes wherein the code forcausing the first wireless communication device to receive thesynchronization information is further configured to receive, from afirst wireless relay device of the one or more wireless relay devices, amessage including at least one of timing information associated with asynchronization reference of the first wireless relay device, frequencyinformation associated with the synchronization reference of the firstwireless relay device, capability information of the first wirelessrelay device, scheduling information of the first wireless relay device,a transmit-receive switching requirement of the first wireless relaydevice, or a synchronization reference switching requirement of thefirst wireless relay device. The computer-readable medium furtherincludes wherein the code for causing the first wireless communicationdevice to receive the synchronization information is further configuredto receive, from a first wireless relay device of the one or morewireless relay devices, a synchronization reference signal that is basedon a synchronization reference of the first wireless relay device. Thecomputer-readable medium further includes wherein the code for causingthe first wireless communication device to receive the synchronizationinformation is further configured to receive priority levels associatedwith sources of the synchronization information, and wherein theadjusting includes adjusting the one or more synchronization referencesbased on the priority levels. The computer-readable medium furtherincludes wherein the code for causing the first wireless communicationdevice to receive the synchronization information is further configuredto receive priority levels associated with hop counts of the one or morewireless relay devices with respect to original sources of correspondingsynchronization references, and wherein the adjusting includes adjustingthe one or more synchronization references based on the priority levels.The computer-readable medium further includes wherein the code forcausing the first wireless communication device to receive thesynchronization information is further configured to receive, from acentral entity, the synchronization information. The computer-readablemedium further includes code for causing the first wirelesscommunication device to receive, from an external synchronizationsource, at least one of timing information or frequency information; andcode for causing the first wireless communication device to adjust theone or more synchronization references further based on the at least oneof timing information or frequency information. The computer-readablemedium further includes wherein the external synchronization sourceincludes at least one of a global positioning system (GPS) or asynchronization source of another radio access technology (RAT). Thecomputer-readable medium further includes code for causing the firstwireless communication device to transmit a message requesting for thesynchronization information. The computer-readable medium furtherincludes code for causing the first wireless communication device totransmit synchronization information associated with the one or moresynchronization references based on at least one of a schedule, asynchronization information request, a measurement of the one or moresynchronization references, or the adjusting of the one or moresynchronization references. The computer-readable medium furtherincludes code for causing the first wireless communication device torelay, to an anchoring wireless communication device that is incommunication with a core network via an optical fiber link, a firstcommunication signal of the communication signals, wherein the code forcausing the first wireless communication device to communicate thecommunication signals is further configured to transmit, to a firstwireless relay device of the one or more wireless relay devices, asecond communication signal based on a downlink transmit timing of theanchoring wireless communication device. The computer-readable mediumfurther includes wherein the code for causing the first wirelesscommunication device to communicating the communication signals isfurther configured to communicate, with a first wireless relay device ofthe one or more wireless relay devices, a second communication signal ofthe communication signals including access traffic. Thecomputer-readable medium further includes code for causing the firstwireless communication device to transmit a message requesting the oneor more wireless relay devices to resynchronize to the one or moreadjusted synchronization references. The computer-readable mediumfurther includes code for causing the first wireless communicationdevice to transmit a configuration for resynchronizing to the one ormore adjusted synchronization references. The computer-readable mediumfurther includes code for causing the first wireless communicationdevice to determine a first gap period based on at least one of acapability parameter of a first wireless relay device of the one or morewireless relay devices, scheduling information of the first wirelessrelay device, a transmit-receive switching requirement of the firstwireless relay device, or a synchronization reference switchingrequirement of the first wireless relay device; and code for causing thefirst wireless communication device to determine a second gap periodbased on at least one a capability parameter of a second wireless relaydevice of the one or more wireless relay devices, scheduling informationof the second wireless relay device, a transmit-receive switchingrequirement of the second wireless relay device, or a synchronizationreference switching requirement of the second wireless relay device, thesecond gap period different from the first gap period. Thecomputer-readable medium further includes wherein the code for causingthe first wireless communication device to communicate the communicationsignals is further configured to transmit, to the first wireless relaydevice, a message indicating the first gap period; transmit, to thesecond wireless relay device, a message indicating the second gapperiod; communicate with the first wireless relay device based on thefirst gap period; and communicate with the second wireless relay devicebased on the second gap period. The computer-readable medium furtherincludes wherein the code for causing the first wireless communicationdevice to communicate the communication signals by switching from anormal cyclic prefix to an extended cyclic prefix based on at least oneof capability parameters of the one or more wireless relay devices,transmit-receive switching requirements of the one or more wirelessrelay devices, synchronization reference switching requirements of theone or more wireless relay devices, or synchronization references of theone or more wireless relay devices. The computer-readable medium furtherincludes wherein the code for causing the first wireless communicationdevice to communicate the communication signals is further configured tocommunicate, with a first wireless relay device of the one or morewireless relay devices, a first communication signal based on a firstsynchronization reference of the one or more synchronization references;and communicate, with a second wireless relay device of the one or morewireless relay devices, a second communication signal based on a secondsynchronization reference of the one or more synchronization referencesthat is different than the first synchronization reference. Thecomputer-readable medium further includes wherein the code for causingthe first wireless communication device to communicate the communicationsignals is further configured to communicate the first communicationsignal in concurrent with the second communication signal. Thecomputer-readable medium further includes wherein the code for causingthe first wireless communication device to communicate the communicationsignals is further configured to communicate, with a first wirelessrelay device of the one or more wireless relay devices, a firstcommunication signal of the communication signals during a first timeperiod based on a first synchronization reference of the one or moresynchronization references; and communicate, with a second wirelessrelay device of the one or more wireless relay devices, a secondcommunication signal of the communication signals during a second timeperiod subsequent to the first time period based on a secondsynchronization reference of the one or more synchronization referencesthat is different than the first synchronization reference.

Embodiments of the present disclosure further include acomputer-readable medium having program code recorded thereon, theprogram code comprising code for causing a central unit to receive, fromone or more wireless relay devices, synchronization informationassociated with the one or more wireless relay devices; code for causingthe central unit to determine a synchronization reference adjustmentbased on at least some of the synchronization information; and code forcausing the central unit to transmit a message to instruct a firstwireless relay device of the one or more wireless relay devices tocommunicate with a second wireless relay device of the one or morewireless relay devices based on the synchronization referenceadjustment.

The computer-readable medium further includes wherein the code forcausing the central unit to receive the synchronization information isfurther configured to receive at least one of frequency informationassociated with synchronization references of the one or more wirelessrelay devices or timing information associated with the synchronizationreferences of the one or more wireless relay devices. Thecomputer-readable medium further includes wherein the code for causingthe central unit to transmit the message is further configured totransmit the synchronization reference adjustment including at least oneof a gap period, a cyclic prefix configuration, a timing synchronizationadjustment, a frequency synchronization adjustment, a transmit timingadjustment, or a receive timing adjustment. The computer-readable mediumfurther includes code for causing the central unit to receive, from theone or more wireless relay devices, reports including at least one ofcapability information of the one or more wireless relay devices,scheduling information of the one or more wireless relay devices,transmit-receive switching requirements of the one or more wirelessrelay devices, synchronization reference switching requirements of theone or more wireless relay devices, or priority levels associated withsynchronization reference sources of the one or more wireless relaydevices; and code for causing the central unit to determine at least oneof the gap period or the cyclic prefix configuration for the firstwireless relay device to communicate with the second wireless relaydevice based on the reports.

Embodiments of the present disclosure further include an apparatuscomprising means (e.g., the transceivers 610 and 710 and antennas 616and 716) for receiving synchronization information associated with oneor more wireless relay devices; means (e.g., processors 602 and 702) foradjusting one or more synchronization references based on at least someof the synchronization information; and means (e.g., the transceivers610 and 710 and antennas 616 and 716) for communicating, with the one ormore wireless relay devices, communication signals based on the one ormore adjusted synchronization references, wherein at least one of thecommunication signals includes backhaul traffic.

The apparatus further includes wherein means for receiving thesynchronization information is further configured to receive, from afirst wireless relay device of the one or more wireless relay devices, amessage including at least one of timing information associated with asynchronization reference of the first wireless relay device, frequencyinformation associated with the synchronization reference of the firstwireless relay device, capability information of the first wirelessrelay device, scheduling information of the first wireless relay device,a transmit-receive switching requirement of the first wireless relaydevice, or a synchronization reference switching requirement of thefirst wireless relay device. The apparatus further includes wherein themeans for receiving the synchronization information is furtherconfigured to receive, from a first wireless relay device of the one ormore wireless relay devices, a synchronization reference signal that isbased on a synchronization reference of the first wireless relay device.The apparatus further includes wherein the means for receiving thesynchronization information is further configured to receive prioritylevels associated with sources of the synchronization information, andwherein the adjusting includes adjusting the one or more synchronizationreferences based on the priority levels. The apparatus further includeswherein the means for receiving the synchronization information isfurther configured to receive priority levels associated with hop countsof the one or more wireless relay devices with respect to originalsources of corresponding synchronization references, and wherein theadjusting includes adjusting the one or more synchronization referencesbased on the priority levels. The apparatus further includes wherein themeans for receiving the synchronization information is furtherconfigured to receive, from a central entity, the synchronizationinformation. The apparatus further includes means (e.g., thetransceivers 610 and 710 and antennas 616 and 716) for receiving from anexternal synchronization source, at least one of timing information orfrequency information, and wherein the means for adjusting the one ormore synchronization references to adjust the one or moresynchronization references further based on the at least one of timinginformation or frequency information. The apparatus further includeswherein the external synchronization source includes at least one of aglobal positioning system (GPS) or a synchronization source of anotherradio access technology (RAT). The apparatus further includes means(e.g., the transceivers 610 and 710 and antennas 616 and 716) fortransmitting a message requesting for the synchronization information.The apparatus further includes means (e.g., the transceivers 610 and 710and antennas 616 and 716) for transmitting synchronization informationassociated with the one or more synchronization references based on atleast one of a schedule, a synchronization information request, ameasurement of the one or more synchronization references, or theadjusting of the one or more synchronization references. The apparatusfurther includes means (e.g., the transceivers 610 and 710 and antennas616 and 716) for relaying, to an anchoring wireless communication devicethat is in communication with a core network via an optical fiber link,a first communication signal of the communication signals, wherein themeans for communicating the communication signals is further configuredto transmit, to a first wireless relay device of the one or morewireless relay devices, a second communication signal based on adownlink transmit timing of the anchoring wireless communication device.The apparatus further includes wherein the means for communicating thecommunication signals is further configured to communicate, with a firstwireless relay device of the one or more wireless relay devices, asecond communication signal of the communication signals includingaccess traffic. The apparatus further includes means (e.g., thetransceivers 610 and 710 and antennas 616 and 716) for transmitting amessage requesting the one or more wireless relay devices toresynchronize to the one or more adjusted synchronization references.The apparatus further includes means (e.g., the transceivers 610 and 710and antennas 616 and 716) for transmitting a configuration forresynchronizing to the one or more adjusted synchronization references.The apparatus further includes means (e.g., processors 602 and 702) fordetermining a first gap period based on at least one of a capabilityparameter of a first wireless relay device of the one or more wirelessrelay devices, scheduling information of the first wireless relaydevice, a transmit-receive switching requirement of the first wirelessrelay device, or a synchronization reference switching requirement ofthe first wireless relay device; and means (e.g., processors 602 and702) for determining a second gap period based on at least one of acapability parameter of a second wireless relay device of the one ormore wireless relay devices, scheduling information of the secondwireless relay device, a transmit-receive switching requirement of thesecond wireless relay device, or a synchronization reference switchingrequirement of the second wireless relay device, the second gap perioddifferent from the first gap period. The apparatus further includeswherein the means for communicating the communication signals is furtherconfigured to transmit, to the first wireless relay device, a messageindicating the first gap period; transmit, to the second wireless relaydevice, a message indicating the second gap period; communicate with thefirst wireless relay device based on the first gap period; andcommunicate with the second wireless relay device based on the secondgap period. The apparatus further includes wherein the means forcommunicating the communication signals is further configured to switchfrom a normal cyclic prefix to an extended cyclic prefix based on atleast one of capability parameters of the one or more wireless relaydevices, transmit-receive switching requirements of the one or morewireless relay devices, synchronization reference switching requirementsof the one or more wireless relay devices, or synchronization referencesof the one or more wireless relay devices. The apparatus furtherincludes wherein the means for communicating the communication signalsis further configured to communicate, with a first wireless relay deviceof the one or more wireless relay devices, a first communication signalbased on a first synchronization reference of the one or moresynchronization references; and communicate, with a second wirelessrelay device of the one or more wireless relay devices, a secondcommunication signal based on a second synchronization reference of theone or more synchronization references that is different than the firstsynchronization reference. The apparatus further includes wherein themeans for communicating the communication signals is further configuredto communicate the first communication signal in concurrent with thesecond communication signal. The apparatus further includes wherein themeans for communicating the communication signals is further configuredto communicate, with a first wireless relay device of the one or morewireless relay devices, a first communication signal of thecommunication signals during a first time period based on a firstsynchronization reference of the one or more synchronization references;and communicate, with a second wireless relay device of the one or morewireless relay devices, a second communication signal of thecommunication signals during a second time period subsequent to thefirst time period based on a second synchronization reference of the oneor more synchronization references that is different than the firstsynchronization reference.

Embodiments of the present disclosure further include an apparatuscomprising means (e.g., the transceivers 610 and 710 and antennas 616and 716) for receiving, from one or more wireless relay devices,synchronization information associated with one or more wireless relaydevices; means (e.g., processors 602 and 702) for determining asynchronization reference adjustment based on at least some of thesynchronization information; and means (e.g., the transceivers 610 and710 and antennas 616 and 716) for transmitting a message to instruct afirst wireless relay device of the one or more wireless relay devices tocommunicate with a second wireless relay device of the one or morewireless relay devices based on the synchronization referenceadjustment.

The apparatus further includes wherein the means for receiving thesynchronization information is further configured to receive at leastone of frequency information associated with synchronization referencesof the one or more wireless relay devices or timing informationassociated with the synchronization references of the one or morewireless relay devices. The apparatus further includes wherein themessage includes the synchronization reference adjustment including atleast one of a gap period, a cyclic prefix configuration, a timingsynchronization adjustment, a frequency synchronization adjustment, atransmit timing adjustment, or a receive timing adjustment. Theapparatus further includes means (e.g., the transceivers 610 and 710 andantennas 616 and 716) for receiving, from the one or more wireless relaydevices, reports including at least one of capability information of theone or more wireless relay devices, scheduling information of the one ormore wireless relay devices, transmit-receive switching requirements ofthe one or more wireless relay devices, synchronization referenceswitching requirements of the one or more wireless relay devices, orpriority levels associated with synchronization reference sources of theone or more wireless relay devices; and means (e.g., processors 602 and702) for determining at least one of the gap period or the cyclic prefixconfiguration for the first wireless relay device to communicate withthe second wireless relay device based on the reports.

As those of some skill in this art will by now appreciate and dependingon the particular application at hand, many modifications, substitutionsand variations can be made in and to the materials, apparatus,configurations and methods of use of the devices of the presentdisclosure without departing from the spirit and scope thereof. In lightof this, the scope of the present disclosure should not be limited tothat of the particular embodiments illustrated and described herein, asthey are merely by way of some examples thereof, but rather, should befully commensurate with that of the claims appended hereafter and theirfunctional equivalents.

What is claimed is:
 1. A method of wireless communication, comprising:receiving, by a first wireless communication device of a multi-hopwireless network, an uplink transmission timing adjustment commandindicating a timing advance between an uplink of the first wirelesscommunication device and a downlink of a second wireless communicationdevice, the second wireless communication device at a next uplink hopfrom the first wireless communication device in the multi-hop wirelessnetwork; transmitting, by the first wireless communication device to thesecond wireless communication device at a transmission time, a firstcommunication signal including backhaul data in an uplink direction, thetransmission time being based on at least the uplink transmission timingadjustment command; and transmitting, by the first wirelesscommunication device to a third wireless communication device of themulti-hop wireless network at a next downlink hop from the firstwireless communication device based on at least the uplink transmissiontiming adjustment command, a second communication signal in a downlinkdirection.
 2. The method of claim 1, wherein the transmitting the secondcommunication signal includes: transmitting, by the first wirelesscommunication device to the third wireless communication device, thesecond communication signal including access data.
 3. The method ofclaim 1, further comprising: receiving, by the first wirelesscommunication device from the third wireless communication device, athird communication signal including backhaul data.
 4. The method ofclaim 1, further comprising: transmitting, by the first wirelesscommunication device to the second wireless communication device, anuplink (UL) communication signal, wherein the transmitting the secondcommunication signal to the third wireless communication device is basedon a timing reference determined with respect to a transmission time ofthe UL communication signal.
 5. The method of claim 1, furthercomprising: receiving, by the first wireless communication device fromthe second wireless communication device, a downlink (DL) communicationsignal, wherein the transmitting the second communication signal to thethird wireless communication device is based on a timing referencedetermined with respect to a transmission time of the DL communicationsignal.
 6. The method of claim 5, further comprising: determining, bythe first wireless communication device, the timing reference based on areception time of the DL communication signal at the first wirelesscommunication device and the uplink transmission timing adjustmentcommand.
 7. The method of claim 1, further comprising: receiving, by thefirst wireless communication device from the second wirelesscommunication device, a downlink (DL) communication signal, wherein thetransmitting the second communication signal is based on a timingreference determined with respect to a reception time of the DLcommunication signal.
 8. The method of claim 1, further comprising:receiving, by the first wireless communication device from the secondwireless communication device, a first downlink (DL) communicationsignal; and receiving, by the first wireless communication device from afourth wireless communication device of the multi-hop wireless network,a second DL communication signal, wherein the transmitting the secondcommunication signal is based on at least one of a reception time of thefirst DL communication signal or a reception time of the second DLcommunication signal.
 9. The method of claim 1, further comprising:receiving, by the first wireless communication device, a secondtransmission timing adjustment command for transmitting an uplink (UL)communication signal to a fourth wireless communication device of themulti-hop wireless network; and transmitting, by the first wirelesscommunication device to the fourth wireless communication device basedon the second transmission timing adjustment command, the ULcommunication signal including backhaul data, wherein the transmittingthe second communication signal is based on at least one of the uplinktransmission timing adjustment command or the second transmission timingadjustment command.
 10. The method of claim 1, wherein the receivingincludes: receiving, by the first wireless communication device from thesecond wireless communication device, the uplink transmission timingadjustment command.
 11. The method of claim 1, wherein the receivingincludes: receiving, by the first wireless communication device from acentral entity, the uplink transmission timing adjustment command. 12.The method of claim 1, further comprising: transmitting, by the firstwireless communication device to the third wireless communication deviceof the multi-hop wireless network, a second transmission adjustmentcommand; and receiving, by the first wireless communication device fromthe third wireless communication device based on the second transmissionadjustment command, an uplink (UL) communication signal.
 13. The methodof claim 1, further comprising: communicating, by the first wirelesscommunication device with the third wireless communication device, athird communication signal based on a first timing reference; andcommunicating, by the first wireless communication device with a fourthwireless communication device, a fourth communication signal based on asecond timing reference that is different than the first timingreference.
 14. An apparatus comprising: a transceiver configured to:receive an uplink transmission timing adjustment command indicating atiming advance between an uplink of the apparatus and a downlink of afirst wireless communication device, wherein the apparatus is associatedwith a multi-hop wireless network, and wherein the first wirelesscommunication device is at a next uplink hop from the apparatus in themulti-hop wireless network; transmit, to a first wireless communicationdevice of the multi-hop wireless network at a transmission time, a firstcommunication signal including backhaul data in an uplink direction, thetransmission time being based on at least the uplink transmission timingadjustment command; and transmit, to a second wireless communicationdevice of the multi-hop wireless network at a next downlink hop from thefirst wireless communication device based on at least the uplinktransmission timing adjustment command, a second communication signal ina downlink direction.
 15. The apparatus of claim 14, wherein the secondcommunication signal includes access data.
 16. The apparatus of claim14, wherein the transceiver is further configured to: receive, from thesecond wireless communication device, a third communication signalincludes backhaul data.
 17. The apparatus of claim 14, wherein thetransceiver is further configured to: transmit, to the first wirelesscommunication device, an uplink (UL) communication signal, wherein thesecond communication signal is transmitted based on a timing referencedetermined with respect to a transmission time of the UL communicationsignal.
 18. The apparatus of claim 14, wherein the transceiver isfurther configured to: receive, from the first wireless communicationdevice, a DL communication signal, wherein the second communicationsignal is transmitted based on a timing reference determined withrespect to a transmission time of the DL communication signal.
 19. Theapparatus of claim 18, further comprising a processor configured to:determine the timing reference based on a reception time of the DLcommunication signal at the apparatus and the uplink transmission timingadjustment command.
 20. The apparatus of claim 14, wherein thetransceiver is further configured to: receive, from the first wirelesscommunication device, a DL communication signal, wherein the secondcommunication signal is transmitted based on a timing referencedetermined with respect to a reception time of the DL communicationsignal.
 21. The apparatus of claim 14, wherein the transceiver isfurther configured to: receive, from the first wireless communicationdevice, a first DL communication signal; and receive, from a thirdwireless communication device of the multi-hop wireless network, asecond DL communication signal, wherein the second communication signalis transmitted based on at least one of a reception time of the first DLcommunication signal or a reception time of the second DL communicationsignal.
 22. The apparatus of claim 14, wherein the transceiver isfurther configured to: receive a second transmission timing adjustmentcommand; and transmit, to a third wireless communication device of themulti-hop wireless network based on the second transmission timingadjustment command, an uplink (UL) communication signal includingbackhaul data, wherein the second communication signal is transmittedbased on at least one of the uplink transmission timing adjustmentcommand or the second transmission timing adjustment command.
 23. Theapparatus of claim 14, wherein the uplink transmission timing adjustmentcommand is received from the first wireless communication device. 24.The apparatus of claim 14, wherein the uplink transmission timingadjustment command is received from a central entity.
 25. The apparatusof claim 14, wherein the apparatus is a base station and the transceiveris further configured to: transmit, to the second wireless communicationdevice of the multi-hop wireless network, a second transmissionadjustment command; and receive, from the second wireless communicationdevice based on the second transmission adjustment command, an uplink(UL) communication signal.
 26. The apparatus of claim 14, wherein thetransceiver is further configured to: communicate, with the secondwireless communication device, a third communication signal based on afirst timing reference; and communicate, with a third wirelesscommunication device, a fourth communication signal based on a secondtiming reference that is different than the first timing reference.